GCSE / O Levels Chemistry

The table gives some information about four redox reactions.
Which row gives correct information about what is oxidised and the evidence that this is
oxidation?
A
B
C
equation
CuO(s) + C(s) CO(g) + Cu(s)
Na(s) + Cl₂(g) → NaCl(s)
N₂(g) + 3H₂(g) → 2NH3(g)
Zn(NO3)2(aq) + Mg(s) Mg(NO3)2(aq) + Zn(s)
what is
oxidised in
the reaction
copper
sodium
nitrogen
zinc
evidence for
this oxidation
copper oxide has given
oxygen to carbon
sodium has
lost an electron
nitrogen has
gained hydrogen
zinc has gained
two electrons

Choice B is correct because:

In the given reaction, sodium (Na) is oxidised. 

Sodium starts as a neutral atom and ends up as a positively charged ion (Na+), meaning it must have lost an electron. 

This is in line with the concept of oxidation where a substance is oxidised when it loses electrons.

Choice A is incorrect because in the reaction, it is carbon (C) that is oxidised, not copper (Cu). This is because carbon (C) gains oxygen to form carbon monoxide (CO), which is a classic sign of oxidation.

Choice C is incorrect because in the reaction, nitrogen (N) is actually reduced, not oxidised. It gains hydrogen to form ammonia (NH3), and gaining hydrogen is a sign of reduction, not oxidation.

Choice D is incorrect because in the reaction, zinc (Zn) is actually reduced, not oxidised. It starts as zinc ion (Zn2+) and ends up as neutral zinc atom (Zn), which means it has gained electrons, and gaining electrons is a sign of reduction, not oxidation.

Redox | 2022 - M/J - 5070/11 | Q24